1. Field of the Invention
This invention relates to a novel broaching tool of the type typically used to produce a round hole or a semi-circle.
2. Description of the Prior Art
Broaching is a machining process whereby one or more cutters with a series of teeth are pushed or drawn entirely across a workpiece and is analogous to single-stroke filing. Broaching is typically carried out on manually-operated presses, on pull-screw machines or on hydraulically actuated broaching machines or presses. The broach has teeth which increase in height towards one end and is typically held in the screw socket of a broaching machine screw or ram by a taper cotter. Usually the first few teeth on the broach are low to permit the small end of the tool to pass through a hole in the workpiece, while the intermediate teeth remove most of the metal and the last few teeth finish the surface to size.
The typical broaching tool presently in use is in the form of an elongated body having a plurality of spaced annular ribs generally transverse to the longitudinal body of the axis. A series of titanium carbide teeth are brazed onto side walls of these ribs in a position perpendicular to the longitudinal body axis. Each of these teeth has a curved upper cutting edge. Of course, when these cutter teeth become worn, it becomes a very expensive proposition to remove the worn teeth and then braze new cutter teeth into position against the ribs. Also, because each cutting edge engages the workpiece at substantially 90.degree., it will be appreciated that immense stresses are placed on the tool and the cutter teeth particularly when broaching metals.
Similar cutting teeth are normally used on rotary milling cutters but recently some rotary milling cutters have been utilizing cutter teeth in the shape of buttons or discs which are indexably mountable on supporting ribs. One such device is described in Saari U.S. Pat. No. 3,540,103, issued Nov. 17, 1970. However, Saari was concerned only with a rotary milling cutter which was specially intended for truing wheels of railroad cars and locomotives.
It will, of course, be appreciated that broaching is a totally different kind of operation from rotary milling in that broaching involves no rotation and is strictly a pushing action similar to single stroke filling. It is the object of the present invention to provide an improved type of broaching tool having easily replaceable and rotatably indexable cutters.